Conveyor systems that merge into a wheel for serially loading containers, such as bottles or tubes, so that the groups or queues of containers can be presented individually for processing can be desirable for automated systems such as those described in Automated Microbial Detection Apparatus, such as described in U.S. 2011/0124028, the content of which is hereby incorporated by reference as if recited in full herein. The height to width ratio of elongated containers such as bottles or tubes can be problematic, particularly when they are provided as mostly unsupported upright containers on a moving floor such as a conveyor. Fallen bottles, if not detected, can jam or cause misfeed errors that can decrease operational speed and/or damage components of the system. One method used to detect fallen bottles employs vertically stacked pairs of front and back sensors to attempt to identify whether test sample containers have fallen. The upper sensor is located at a position that is higher than a diameter of the bottle while the lower sensor is positioned no higher than the diameter of the bottle. If a bottle tips or falls over, the lower sensor is triggered while the upper one is not. This “fault condition” can be used to generate an operator alert. However, where there are queues of more than one container deep and one has fallen over with another upright container behind it, the upper sensor may detect the upright bottle, so the stacked pair of sensors then fails to detect the fault. Also, the reflective nature of transparent or translucent materials such as glass or polymer containers (e.g., plastic) can have labels applied to the container, varying fluid content, orientations and the like that can that can alter detection reliability.